LONDON — It was a royal day at the races, as Queen Elizabeth II watched a horse with the courtly name of Camelot win the Epsom Derby — the kickoff to a four-day celebration of the British monarch's 60 years on the throne.

The derby was held Saturday. Later in the weekend the queen will make a trip down the River Thames, and then take in a concert — all accompanied by tens of thousands of her subjects, coming out to fete a monarch whose longevity has given her the status of the nation's favourite grandmother.

An armada of vessels — from historic sailboats and barges to kayaks, lifeboats and military launches — was mustering along the Thames ahead of Sunday's river pageant. The queen aboard the royal barge will lead the flotilla of 1,000 boats — described by organizers as the biggest gathering on the river for 350 years.

Diamond Jubilee festivities officially began Saturday with a 41-gun salute fired by the King's Troop, Royal Horse Artillery at Horse Guards Parade in central London.

The 86-year-old monarch and her husband, Prince Philip, visited Epsom racecourse south of the capital for the Derby, one of the year's biggest horse-racing meetings. The queen waved to the 130,000-strong crowd as she was driven down the racecourse in a Bentley bearing the Royal Standard — the car's sun roof kept shut under grey skies — before settling down to watch the races from the royal box.

Dressed in a royal blue coat and matching hat over a blue-and-white floral dress, the queen was accompanied by members of the royal family including her sons Prince Andrew and Prince Edward and Andrew's daughters Princess Beatrice and Princess Eugenie.

The royals were treated to an aerial display by members of the British Army's Red Devils parachute team before the main event — the racing.

The monarch is a racing fan and horse breeder who has attended the Derby for decades and reads the Racing Post each day over breakfast, although unlike many of her subjects she does not gamble.

The queen presented prizes to some of the race winners and spoke intently to jockeys and trainers

“She's incredibly knowledgeable. Her knowledge of thoroughbreds and breeding goes way back,” said Anthony Cane, chairman of Epsom Downs Racecourse.

The queen took the throne in 1952 on the death of her father, King George VI, and most Britons have known no other monarch.

Despite cool, damp weather in much of the country, hundreds of thousands of people are expected to participate in celebrations, including street parties, Sunday's flotilla and a Monday pop concert in front of Buckingham Palace featuring Elton John and Paul McCartney.

Jubilee events end Tuesday with a religious service at St. Paul's Cathedral, a carriage procession through the streets of London and the queen's appearance with her children, grandchildren and great-grandchildren on the palace balcony.

Prime Minister David Cameron — the 12th British leader of the queen's reign — paid tribute to the monarch's “extraordinary level of physical energy, mental energy, and above all devotion to her people, to the institutions of this country, to the way our democracy works.”

Not everyone in Britain will be celebrating. The anti-monarchist group Republic plans a riverbank protest as the flotilla goes by on Sunday, followed by a pub night where royal refuseniks can drown their sorrows.

With pictures of the monarch splashed across newspaper front pages, the left-leaning Guardian provided a button on its website that removed all jubilee stories.

But many Britons embraced the jubilee spirit — a tribute to a monarch whose popularity cuts across all ages, social classes and political affiliations.

In a jubilee gift from Britain's politicians, lawmakers from the three main parties have backed a motion calling for the tower housing Big Ben — the beloved London bell that chimes the quarter hour — to be renamed in the queen's honour.

More than half of legislators have signed a letter asking parliamentary authorities to consider renaming the east tower of the Houses of Parliament the Elizabeth Tower. It's currently called the Clock Tower.

While many Britons used the long weekend to relax — and an estimated two million left the country on vacation — writers and religious leaders used the occasion to reflect on how Britain has changed over the queen's reign, from a war-scarred imperial power to a middle-sized power with oversized cultural clout.

Archbishop of Canterbury Rowan Williams, spiritual head of the Anglican Church, expressed a widely held view when he said Britain had been lucky to have Elizabeth as monarch throughout a period of rapid change.

“It seems to me that what her importance has been for most people in this country has been as a sign of stability, a sign of some kind of security,” Williams said in a jubilee video message.

“And that wouldn't have happened had she not been so profoundly committed at every point, so intelligently committed to understanding the society she was in, working with the flow of the changes that have taken place. To have someone who has been a symbol, a sign of stability through all that period is really a rather exceptional gift.”

Some have speculated that as she ages the queen might abdicate in favour of her 63-year-old son, Prince Charles — or even her wildly popular grandson, Prince William.

Those who know her say that is unlikely.

“I think it's an absolutely absurd notion,” former prime minister John Major told Sky News. “I have not a shadow of a doubt that given her health she will remain monarch for the rest of her life.”